1. Field of the Invention
The present invention relates to an activation control device for a steam turbine plant.
2. Description of the Related Art
Renewable energy for power generation is typified by wind power generation and solar power generation. For a power plant using such renewable energy, the amount of electric power generated from renewable energy greatly varies depending on seasons, weather, and the like. Thus, this kind of power plant provided with a steam turbine needs to further reduce the time it takes for activation (or activate the power plant at a high speed) in order to suppress a variation in the power generation amount for stabilization of the power plant.
Upon the activation of the power plant, since the temperature and amount of steam flowing in the steam turbine rapidly increase, the temperature of a front surface of a turbine rotor rapidly increases, compared with the inside of the turbine rotor. As a result, stress (thermal stress) due to the difference between the surface of the turbine rotor and the inside of the turbine rotor increases. Since excessive thermal stress may reduce the life of the turbine rotor, it is necessary to suppress the increased thermal stress to a preset limit or lower. In addition, in the activation of the steam turbine, the turbine rotor and a casing storing the turbine rotor are exposed to high-temperature steam, thereby heated, and elongate (thermal elongation) by thermal expansion in a direction in which a turbine shaft extends. Since the turbine rotor and the casing are different from each other in the structure and in the heat capacity, the difference in the thermal elongation (thermal elongation difference) occurs between the turbine rotor and the casing. If the thermal elongation difference increases, the turbine rotor that is a rotary body and the casing that is a stationary body may contact each other and be damaged. It is, therefore, necessary to suppress the thermal elongation difference to a preset limit or less. Since there are some constraints for the activation of the steam turbine, it is necessary to control the activation while satisfying the constraints.
As an activation control method of this type, there is a method in which an activation mode is determined based on a time elapsed after the stop of a power plant, that is an elapsed time after the power plant is stopped, and the activation of the power plant is controlled based on an activation schedule determined for each of activation modes (refer to Non-Patent Document 1: “Shoji Hiraga: “Automatic Thermal Power Plant Starting Device”, Hitachi Hyoron, Vol. 48, No. 6, 763-767 pp. (1966)” and the like). In addition, there is another method in which the activation of a gas turbine and the activation of a steam turbine are controlled based on a measured temperature of a casing metal arranged at a stage of the steam turbine in order to suppress the occurrence of thermal stress (refer to Japanese Patent No. 4208397 and the like). In addition, there is still another method in which activation patterns are switched among activation patterns such as a pattern prioritizing a time required for activation, a pattern prioritizing an efficiency, based on needs for activation (refer to Non-Patent Document 2: “L. Balling: Fast cycling and rapid start-up: new generation of plants achieves impressive results, Modern Power Systems, January (2010)”, Japanese Patent No. 4885199, and the like). In addition, there is still another method in which an increase rate of the temperature of steam to be supplied to a steam turbine is defined and a plant is controlled based on the increase rate of the temperature (refer to Non-Patent Document 3: “C. Ruchti et al.: Combined Cycle Power Plants as ideal solution to balance grid fluctuations, Krafwerkstechnisches Kolloquium, T U Dresden, 18-19, September (2011)” and the like). In addition, there is still another method in which thermal stress and a thermal elongation difference for a certain time period from a current time to a future time are predicted and an activation schedule is obtained that enables a steam turbine to be activated at a high speed while suppressing the predicted thermal stress to a limit or lower (refer to Non-Patent Document 4: “Shigeru Matsumoto and other 2 people: Optimum Turbine Startup Methodology Based on Thermal Stress Predition, Vol. 61, No. 9 p. 798-803 (September, 2010)”, Japanese Patent No. 4723884, JP-2009-281248-A, JP-2011-111959-A, and the like).